A tightener drive for tightening a seatbelt causes belt slack in the seatbelt to be eliminated in the event of a crash. The tightener drive is activated in a known manner by a vehicle sensor, an electric igniter serving to ignite a propellant for the tightener drive. Up to now, in the event of a crash, all tightener drives allocated to the vehicle seats are activated regardless of whether or not a particular vehicle seat is occupied.